In recent years, as manufacturing process of a semiconductor integrated circuit is minimized, power supply noise increasingly affects operation of the semiconductor integrated circuit, for example, erroneous operation due to an effect of power supply noise on a minimized circuit wiring. In order to cope with the power supply noise, first, it is preferable to accurately observe the power supply noise that causes the malfunction.
As the observation method of the power supply noise, a method to connect an oscilloscope to a semiconductor integrated circuit or an electronic board that mounts the semiconductor integrated circuit via a probe and perform observation is disclosed. Such a method of connecting the oscilloscope to the outside of the semiconductor integrated circuit and perform the observation has the following drawback. For example, it is difficult to observe high frequency power supply noise generated in a semiconductor integrated circuit such as a central processing unit (CPU), which has an arithmetic processing unit that operates at a high speed, or a chip set that operates with the CPU at a high speed from the outside of the semiconductor integrated circuit. That is, the high frequency power supply noise is not only easily attenuated but also has an insignificant random pattern different from normal signals. Accordingly, it is difficult to observe the high frequency power supply noise generated in the semiconductor integrated circuit using the oscilloscope connected to the outside of the semiconductor integrated circuit. Consequently, in order to facilitate the observation of the high frequency power supply noise, a technology to mount a circuit for performing observation of power supply noise on a semiconductor integrated circuit by on-chip has been proposed. See, for example, Japanese Laid-open Patent Application No. 2005-249408, and Japanese Laid-open Patent Application No. 2004-212387.